Replace Engine

[Penns Beach]

I have a 2003 2700scr with a 350 5.7 MPI with Bravo III. If I wanted to replace this engine with another one what is the largest engine I can install? Would there be much modifications (ie engine mounts, etc...)? Even if you think I am crazy what all would there be involved in this change out.

[pascavone]

7.4 MPI is 325 HP and would fit.

the 8.1 is the same engine boar over.

The new 6.2 is suppose to give you 320 HP but I don;t believe it.

you need to call mercrusier and see if the engine mounts and transom mounts are the same.

If not better to go buy another boat.

[shrew]

The dimensions on the 5.7L and 6.2L are the same. I would suspect these are basically the same block and would be a direct bolt in. As stated, check with Merc. first. This is much like the 7.4, 8.1, and 8.2L all having the same footprint and motor mount locations as well.

Merc is claiming:

5.7L MPI = 300HP (860lbs)
6.2L MPI = 325HP (860lbs)
8.1L MPI = 370HP (1130lbs)
8.2L MPI = 375hp (1180lbs)

You're only going to find an aftermarket or rebuilt in a 7.4, Merc doesn't make them anymore. The 7.4 were only 300-325 HP anyway. An 8.1/8.2 would go like crazy, but be about 200lbs (25%)heavier.

[GlennW]

Stay with the 5.7, you have limitless possibilties and keeping the weight the same. There are many performance companies out there that mass produce these from 300- 450+ HP, or even more.
You actually will use less fuel on a higher HP and Torque engine at cruise than you will with a stock motor.
It takes torque and HP to move a boat, having more of these at lower RPM's gives you better performance and fuel economy.
I would recommend staying under 375 or so HP.
Going Big Block you will need to change out gear ratio or over compensate with a bigger wheel.(prop)